1. Field of the Invention
This invention relates to railroad crossties and, more particularly, to novel systems and methods for construction thereof from composite structural materials.
2. Background Art
Railroad crossties, sometimes called rail ties or simply ties, have traditionally been constructed of wood. Wood provides a structural platform sitting on top of road ballast, rock of specified size distribution. The crosstie provides sufficient “flotation” (load pressure distribution) to support the substantial weight of the axles of a railroad train passing over the top thereof. Each rail is secured near one end of each crosstie in order to provide support for a train.
In traditional embodiments, rail ties have been cut from or formed of various wood products, including hardwoods such as oak, as well as softer woods such as pine or spruce. Typically, rail ties have been treated with creosote, a thick, oily liquid that is highly viscous and is typically soaked into the rail ties as an insecticide or pesticide to prevent or resist rotting of the wood.
Over time, the spikes that have secured plates to the ties, may eventually begin to loosen. As wood weathers, splits, shrinks, and the like, the spikes may loosen. Accordingly, the base plate underneath each rail, on top of a tie, as well as the securement plates that attach over the top of the base of the rail, may work loose and fail to provide adequate securement.
In due course, railroad ties are typically removed and replaced by road crews working along the railroad tracks.
In more recent years, various proposals have succeeded in converting some railroad ties to composite materials, such as fiberglass and the like. Similarly, proposals for rubber rail ties have been made. Concrete ties are used in various mass transit rail systems, but appear to be more common in light rail systems, rather than in the heavy or freight rail systems.
Meanwhile, recycling of the rubber from tires has become a major storage and remanufacturing issue. To this end, recycled crumb rubber (RCR) has been developed. Recycled crumb rubber is made up of the ground up rubber material from tires, usually absent the fibrous cord materials, such as nylon and rayon, or other polymer cords, and substantially devoid of any of the metals that previously formed the bead and the radial bands of seal reinforced tires.
It would be an advance in the art to provide a suitable composite tie having suitable protection against weather, suitable strength, selectable weight or density, suitable strength, and reproducible manufacturing.
It would also be an advance in the art to provide a process and product that may be manufactured by mass production techniques, using combinations of polymers, reinforcement within a polymer matrix, suitable fill materials having densities and strengths necessary and suitable for resisting buckling of a fiber reinforced shell, supporting loads within the shell of a tie, and providing suitable weight, as well as anchoring for fasteners securing rails thereto.
It would also be an advance in the art to provide a tie that performs suitably in service to resist any tendency toward moving with respect to ballast, that is, for example, providing a suitable degree of lateral ballast resistance against lateral motion of the railroad on the underlying ballast.